A sub-frame for supporting a suspension arm may be situated below a main frame which forms a part of a vehicle body (c.f. JP 2015-231781 A). The sub-frame disclosed in JP 2015-231781 A includes a pillar member, a set plate and a crash can. The crash can is fixed to the set plate and extends forward from the set plate. When there is a collision of an automobile, the crash can is compressively deformed to absorb an impact force acting on the automobile.
The pillar member includes two attachment plate portions and a pillar portion. The attachment plate portion on the left side is away from the attachment plate portion on the right side. The pillar portion is formed by a thin plate having a horizontal cross-section bulging rearward from the left and right attachment plate portions. The pillar portion extends in the vertical direction. The pillar portion is connected to a vehicle body situated above the sub-frame. The aforementioned set plate is connected to the left and right attachment plate portions by screws. Since the pillar portion has a horizontal cross-section bulging rearward from the left and right attachment plate portions, the pillar portion may have a high rigidity. Since the crash can is connected to the highly rigid portion, only the crash can is compressively deformed so that portions situated on the rear side of the crash can are less likely to be damaged when an impact force is not so large. Since the set plate is connected to the left and right attachment plate portions by screws, deformation which may move the left and right attachment portions toward or away from each other is less likely to occur. Therefore, the pillar member may receive a large impact force with little deformation.
When collusion occurs in a portion outside a position where the crash can is situated, the automobile designed on the basis of the techniques disclosed in JP 2015-231781 A hardly causes deformation of the crash can. Consequently, an impact force may be transmitted to a cabin without substantial reduction.
JP 2013-212757 A proposes techniques for preventing transmission of an impact force to a cabin, the impact force being caused by collision outside a position where a crash can is situated. A sub-frame disclosed in JP 2013-212757 A includes a crash can, two set plates, a front side member and a projecting member. The crash can is fixed to one of the two set plates (hereinafter, referred to as “first set plate”). The other of the two set plates (hereinafter, referred to as “second set plate”) is fixed to a front end of the front side member. The second set plate is situated on the rear side of the first set plate so as to overlap the first set plate.
The front side member extends rearward from the second set plate. The projecting member projects outward in the vehicle width direction from the front side member. The second set plate extends outward in the vehicle width direction from the first set plate to cover a front end of the projecting member.
A collision object colliding with the automobile outside the crash can hits with the second set plate which forms a flat plane in front of the projecting member. An impact force is then, transmitted from the second set plate to the projecting member. The impact force transmitted to the projecting member acts as a force for bending the front side member. As a result of bending the front side member, the impact force is alleviated. Therefore, the cabin is appropriately protected from the impact force.
When the techniques disclosed in JP 2015-231781 A and JP 2013-212757 A are combined, a sub-frame may protect a cabin from various impacts. However, combining the techniques disclosed in JP 2015-231781 A and JP 2013-212757 A requires a set plate, to which a crash can is fixed, and a set plate for covering a front end of a projecting member. In this case, it is necessary to join these set plates and to join the set plate for covering the front end of the projecting member to a pillar member. As a result of forming many joining portions, it becomes cumbersome to manufacture the sub-frame.
When joining all members including two set plates, a pillar member, a projecting member and a crash can depends on welding techniques, it is necessary to weld these members at respective joining positions with high reliability. This means that well-skilled welding techniques are required. In addition, when there is inappropriate connection of a set plate to a pillar member, an impact force transmitted to the projecting member may not be effectively used in bending a front side member.
An object of the present invention is to provide a front chassis structure configured to protect a cabin from various impacts, the front chassis structure being easily manufactured.